Bharat Prashar Department of Pharmaceutical Sciences, Manav Bharti University, Solan (H.P) *shashi_ranaute@yahoo.in ABSTRACT: In this review article, we discussed abouteffluent testing and treatment in pharmaceutical industry,Biological treatment of wastewater is frequently the most beneficial method for selecting various toxic compounds from the environment. Most of the organic compounds in industrial wastewaters are of natural origin and can be degraded by common bacteria in aerobic or anaerobic processes. The composition of these wastewaters is very variable. A great variety of organic chemicals can be determined among the principal components of these types of wastewaters. Antibiotics are the major group of pharmaceuticals. Among all the other pharmaceutical drugs and substances, antibiotics are important compounds due to its serious irreversible increase the release to the environment[1][2][3][4][5] INTRODUCTION:Biological treatment of wastewater is frequently the most beneficial method for selecting various toxic compounds from the environment. Most of the organic compounds in industrial wastewaters are of natural origin and can be degraded by common bacteria in aerobic or anaerobic processes. “Due to its proven capacity to degrade certain toxic components as well as most common organic pollutants in industrial wastewater, anaerobic treatment today has advanced to a high level of usefulness in the restoration of many industrial effluents” ( Donlon, Flores, Field & Lettinga, 1995). The pharmaceutical industry constitutes from the wastewaters containing toxic organic chemicals. The composition of these wastewaters is very variable. A great variety of organic chemicals can be determined among the principal components of these types of wastewaters. Antibiotics are the major group of pharmaceuticals. Among all the other pharmaceutical drugs and substances, antibiotics are important compounds due to its serious irreversible increase the release to the environment. Antibiotics are in effluent of treatment plants and receiver media due to difficult treatability with conventional treatment systems such as aerobic active sludge system. For that reason, they spoil ecological balance to form toxicity to organisms in ecosystem and biological treatment systems. Objectives and Scopes The purpose of this study is to provide the treatability of two types of antibiotics (Kemicetine and Sulfamerazine) in an up flow anaerobic sludge blanket (UASB) reactor / aerobic completely stirred tank (CSTR) reactor and an anaerobic baffled (ABR) reactor / aerobic (CSTR) reactor systems. There is not enough knowledge about the treatability of pharmaceutical wastewater in anaerobic conditions. Furthermore, no study about the treatability of wastewaters containing antibiotic was encountered using both UASB and ABR reactors. Therefore this thesis was designed to investigate these lacks in the literature. The major objectives of this research can be summarized as follows; 1. to investigate the removal efficiencies COD and BOD5, VFA production, total and methane gas productions of synthetic wastewaters containing antibiotic in different Kemicetine and Sulfamerazine doses in sequential UASB/ CSTR and ABR/ CSTR reactor systems, 2. to monitor the toxicity of synthetic wastewater containing antibiotic based on specific methanogenic activity (SMA) tests, 3. to characterize the wastewater composition based on inert COD, slowly and readily biodegradable organic substances and BOD5 / COD ratios, 4. to compare both systems according to their treatment efficiencies. Physiochemical measurement:Temperature Measured using pH and dissolved oxygen meter, or thermometer.

pH “acidity” of the water, measured using a pH meter. This meter is used to measure the acidity of the water by comparing readings from a reference electrode and a sample electrode. To determine pH the output of these electrodes must be temperaturecompensated, most pH meters also measure temperature.

Turbidity The clarity of the water, measured using a portable turbidimeter. The turbidimeter measures the light transmittance of a sample in NTU's (Nephelometric Turbidity Units, a standard measure). It needs no field calibration. Handle the sample vials only by their

ends (preferably the lid) so as not to affect the transmittance; wipe any fingerprints, spots, etc. from the outside of the vial; and be sure to close the vial-compartment lid when taking a measurement.

The DO meter will measure dissolved oxygen, electrical conductivity, and salinity. DO is measured by the rate of consumption of oxygen at the tip of the probe, so it requires continual movement of water past the tip (an up-and-down motion seems to work best, keep the probe tip submerged). Stable readings are not possible while the temperature of the sample is changing. When performing analysis at multiple sampling locations, the DO meter calibration should be checked at the beginning, middle, and end of each analysis day. Oxygen from the atmosphere enters water through adsorption at its surface, a process enhanced by agitation (rapid moving water). In flowing water, oxygen-rich water at the surface is constantly being replaced by water containing less oxygen as a result of turbulence, creating a greater potential for exchange of oxygen across the air-water interface. Flowing water is more likely to have high DO levels than stagnant water Because still water undergoes less internal mixing, the upper layer of oxygen-rich water tends to stay at the surface, resulting in lower dissolved oxygen levels throughout the rest of the water levelsDO can also enter water as a waste product of photosynthesis by aquatic plants, a process highly dependant on sunlight.The amount of oxygen that can be held by water depends on the water temperature, salinity, and pressure.Gas solubility increases with decreasing temperature and decreasing salinityColder water can hold more oxygen than warm water and freshwater can hold more oxygen than saltwater.Gas solubility decreases as pressure decreases so the amount of oxygen absorbed in water decreases as altitude increases. Winkler method :The Winkler method for the determination of dissolved O2 involves adding an excess of „white‟ Mn(OH)2 which contains Mn2+ ions.

For every molecule of O2 two molecules of I2 are formedThe quantity of iodine present can be found though titration of the sample with sodium thiosulphate. Biochemical oxygen demand or BOD :-BOD refers to the amount of oxygen that would be consumed if all the organic material in 1 L of water (or wastewater or industrial effluent) were oxidized by microbes chemical procedure for determining the amount of dissolved oxygen needed by aerobic biological organisms in a body of water to break down organic material present in a given water sample at certain temperature over a specific time period. It is not a precise quantitative test, although it is widely used as an indication of the organic quality of water. It is most commonly expressed in milligrams of oxygen consumed per litre of sample during 5 days of incubation at 20 C and is often used as a robust surrogate of the degree of organic pollution of water. There are two commonly recognized methods for the measurement of BOD. Dilution method To ensure that all other conditions are equal, a very small amount of micro-organism seed is added to each sample being tested. This seed is typically generated by diluting activated sludge with de-ionized water. The BOD test is carried out by diluting the sample with oxygen saturated de-ionized water, inoculating it with a fixed aliquot of seed, measuring the dissolved oxygen (DO) and then sealing the sample to prevent further oxygen dissolving in. The sample is kept at 20 °C in the dark to prevent photosynthesis (and thereby the addition of oxygen) for five days, and the dissolved oxygen is measured again. The difference between the final DO and initial DO is the BOD. The apparent BOD for the control is subtracted from the control result to provide the corrected value.

The loss of dissolved oxygen in the sample, once corrections have been made for the degree of dilution, is called the BOD 5. For measurement of carbonaceous BOD (cBOD), a nitrification inhibitor is added after the dilution water has been added to the sample. The inhibitor hinders the oxidation of nitrogen. BOD can be calculated by: * Undiluted: Initial DO - Final DO = BOD * Diluted: ((Initial DO - Final DO)- BOD of Seed) x Dilution Factor BOD is similar in function to chemical oxygen demand (COD), in that both measure the amount of organic compounds in water. However, COD is less specific, since it measures everything that can be chemically oxidised, rather than just levels of biologically active organic matter. Manometric method This method is limited to the measurement of the oxygen consumption due only to carbonaceous oxidation. Ammonia oxidation is inhibited. The sample is kept in a sealed container fitted with a pressure sensor. A substance that absorbs carbon dioxide (typically lithium hydroxide) is added in the container above the sample level. The sample is stored in conditions identical to the dilution method. Oxygen is consumed and, as ammonia oxidation is inhibited, carbon dioxide is released. The total amount of gas, and thus the pressure, decreases because carbon dioxide is absorbed. From the drop of pressure, the sensor electronics computes and displays the consumed quantity of oxygen. The main advantages of this method compared to the dilution method are: * simplicity: no dilution of sample required, no seeding, no blank sample * direct reading of BOD value * continuous display of BOD value at the current incubation time. Furthermore, as the BOD measurement can be monitored continuously, a graph of its evolution can be plotted. Interpolation of several graphs on a similar water may build an experience of its usual evolution, and allow an estimation of the five days BOD after as early as the first two days of incubation. Chemical oxygen demand (COD) :- test is commonly used to indirectly measure the amount of organic compounds in water. Most applications of COD determine the amount of organic pollutants found in surface water (e.g. lakes and rivers), making COD a useful measure of water quality. It is expressed in milligrams per liter (mg/L), which indicates the mass of oxygen consumed per liter of solution. Older references may express the units as parts per million (ppm). The basis for the COD test is that nearly all organic compounds can be fully oxidized to carbon dioxide with a strong oxidizing agent under acidic conditions. The amount of oxygen required to oxidize an organic compound to carbon dioxide, ammonia, and water is given by:

This expression does not include the oxygen demand caused by the oxidation of ammonia into nitrate. The process of ammonia being converted into nitrate is referred to as nitrification. The following is the correct equation for the oxidation of ammonia into nitrate.

The second equation should be applied after the first one to include oxidation due to nitrification if the oxygen demand from nitrification must be known. Dichromate does not oxidize ammonia into nitrate, so this nitrification can be safely ignored in the standard chemical oxygen demand test. The International Organization for Standardization describes a standard method for measuring chemical oxygen demand in ISO 6060. Hazardous Waste Treatment Technologies: Even with after vigorous hazardous waste reduction program, there will still be large quantities of hazardous wastes that will require treatment and disposal. The treatment technologies have been categorised as physical, chemical, biological, thermal, or stabilization /fixation. Physical treatment processes include gravity separation, phase change systems, such as air and steam stripping of volatiles from liquid wastes, and various filtering operations, including carbon adsorption. Chemical treatment transforms waste into less hazardous substances using such techniques as pH neutralisation, oxidation or reduction, and precipitation. Biological treatment uses microorganisms to degrade organic compounds in the waste stream. Thermal destruction processes include incineration, which is increasingly becoming a preferred option for the treatment of hazardous wastes, and pyrolysis, which is the chemical decomposition of waste is brought about by heating the material in the absence of oxygen. Stabilisation techniques involve removal of excess of water from a waste and solidifying the remainder either by mixing it with a stabilising agent such as portland cement, or vitrifying it to a glassy substance. Most treatment measures have both physical and chemical aspects. The appropriate treatment technology for the hazardous wastes depends on the nature of the wastes. The type of physical treatment to be applied to wastes depends strongly upon the physical properties of the material treated, including the state of matter, solubility in water and organic solvents, density, volatility, boiling point and melting point. Treatments Operations Screening Sedimentation Primary Equalization Neutralisation Mechanical flocculation & Chemical coagulation Aerated lagoon Trickling filtration Secondary Activated sludge process Oxidation ditch & pond Anaerobic digestion Oxidation technique Tertiary Electrolytic precipitation & Foam fractionation Membrane technologies

Electrochemical processes Ion exchange method Photo catalytic degradation Adsorption (Activated Carbon etc.) Thermal evaporation Primary Treatment { physical treatments} :After the removal of gross solids, gritty materials and excessive quantities of oil and grease, the next step is to remove the remaining suspended solids as much as possible. This step is aimed at reducing the strength of the waste water and also to facilitate secondary treatment. Screening: Coarse suspended matters such as rags, pieces of fabric, fibres, yarns and lint are removed. Bar screens and mechanically cleaned fine screens remove most of the fibres. The suspended fibres have to be r moved prior to secondary biological treatment; otherwise they may affect the secondary treatment system. They are reported to clog trickling filters, seals or carbon beads. Sedimentation: Sedimentation is a physical process where by particles suspended in a liquid settle by means of gravity. The fundamental elements of most sedimentation processes are: • a basin or container of sufficient size to maintain the liquid to be treated in a relatively quiescent state for a specified period of time • a means of directing the liquid to be treated into the above basin in a manner conducive to settling. • a means of physically removing the settled particles from the liquid. Sedimentation can be either a batch or a continuous process. Continuous processes are by far the most common, particularly when large volumes of liquid are to be treated. This technique has been widely used in the removal of heavy metals from iron and steel industry waste water; removal of fluoride from aluminium production waste water; and removal of heavy metals from waste water from copper smelting and from metal finishing industry and waste water stream from organic chemicals. The suspended matter in effluent can be removed efficiently and economically by sedimentation. This process is particularly useful for treatment of wastes containing high percentage of settable solids or when the waste is subjected to combined treatment with sewage. The sedimentation tanks are designed to enable smaller and lighter particles to settle under gravity. The most common equipment used includes horizontal flow sedimentation tanks and centre-feed circular clarifiers. The settled sludge is removed from the sedimentation tanks by mechanical scrapping into hoppers and pumping it out subsequently. Equalization: Effluent streams are collected into „sump pit‟. Sometimes mixed effluents are stirred by rotating agitators or by blowing compressed air from below. The pit has a conical bottom for enhancing the settling of solid particles. Neutralisation: Normally, pH values of cotton finishing effluents are on the alkaline side. Hence, pH value of equalized effluent should be adjusted. Use of dilute sulphuric acid and boiler flue gas rich in carbon dioxide are not uncommon. Since most of the secondary biological treatments are effective in the pH 5 to 9, neutralisation step is an important process to facilitate. Chemical coagulation and Mechanical flocculation: Finely divided suspended solids and colloidal particles cannot be efficiently removed by simple sedimentation by gravity. In such cases, mechanical flocculation or chemical coagulation is employed. In mechanical flocculation, the textile waste water is passed through a tank under gentle stirring; the finely divided suspended solids coalesce into larger particles and settle out. Specialized equipment such as clari flocculator is also available, wherein flocculation chamber is a part of a sedimentation tank. In order to alter the physical state of colloidal and suspended particles and to facilitate their removal by sedimentation, chemical coagulants are used. It is a controlled process, which forms a floc (flocculent precipitate) and results in obtaining a clear effluent free from matter in suspension or in the colloidal state. The degree of clarification obtained also depends on the quantity of chemicals used. In this method, 80-90% of the total suspended matter, 40-70% of BOD, 5days, 30-60% of the COD and 80-90% of the bacteria can be removed. However, in plain sedimentation, only 50-70% of the total suspended matter and 30-40% of the organic matter settles out. Most commonly used chemicals for chemical coagulation are alum, ferric chloride, ferric sulphate, ferrous sulphate and lime.

Secondary Treatment The main purpose of secondary treatment is to provide BOD removal beyond what is achievable by simple sedimentation. It also removes appreciable amounts of oil and phenol. In secondary treatment, the dissolved and colloidal organic compounds and colour present in waste water is removed or reduced and to stabilize the organic matter. This is achieved biologically using bacteria and other microorganisms. Textile processing effluents are amenable for biological treatments [3]. These processes may be aerobic or anaerobic. In aerobic processes, bacteria and other microorganisms consume organic matter as food. They bring about the following sequential changes: (i) Coagulation and flocculation of colloidal matter (ii) Oxidation of dissolved organic matter to carbon dioxide (iii) Degradation of nitrogenous organic matter to ammonia, which is then converted into nitrite and eventually to nitrate. Anaerobic treatment is mainly employed for the digestion of sludge. The efficiency of this process depends upon pH, temperature, waste loading, absence of oxygen and toxic materials. Some of the commonly used biological treatment processes are described below: Aerated lagoons:These are large holding tanks or ponds having a depth of 3-5 m and are lined with cement, polythene or rubber. The effluents from primary treatment processes are collected in these tanks and are aerated with mechanical devices, such as floating aerators, for about 2 to 6 days. During this time, a healthy flocculent sludge is formed which brings about oxidation of the dissolved organic matter. BOD removal to the extent of 99% could be achieved with efficient operation. The major disadvantages are the large space requirements and the bacterial contamination of the lagoon effluent, which necessitates further biological purification. In aerated lagoons, oxygen is supplied mainly through mechanical or diffused aeration rather than by algal photosynthesis. Aerated lagoons typically are classified by the amount of mixing provided. A partial mix system provides only enough aeration to satisfy the oxygen requirements of the system and does not provide energy to keep all total suspended solids (TSS)in suspension. Aerated lagoons can reliably produce an effluent with both biological oxygen demand (BOD) and TSS < 30mg/L if provisions for settling are included at the end of the system. Significant nitrification will occur during the summer months if adequate dissolved oxygen is applied. Many systems designed only for BOD removal fail to meet discharge standards during the summer because of a shortage of dissolved oxygen. Nitrification of ammonia and BOD removal occur simultaneously and systems can become oxygen limited. To achieve nitrification in heavily loaded systems, pond volume and aeration capacity beyond that provided for BOD removal are necessary. Oxygen requirements for nitrification are more demanding than for BOD removal. It is generally assumed that 1.5 kg of oxygen is required to treat 1 kg of BOD. About 5 kg of O2 aretheoretically required to convert 1 kg of ammonia to nitrate. Algae Removal from Lagoon Effluent: Ferrate could be considered for treatment and removal of algae from facultative lagoon effluents. Concomitant with effluent treatment and disinfection, the Fe(III) by-product can promote coagulation of microscopic algae that can facilitate removal by settling or filtration. Experimental testing would be required to determine technical and economic feasibility. Trickling filters:A trickling filter consists of a fixed bed of rocks, lava, coke, gravel, slag, polyurethanefoam, sphagnum peat moss, ceramic, or plastic media over which sewage or other wastewater flows downward and causes a layer of microbialslime (biofilm) to grow, covering the bed of media. Aerobicconditions are maintained by splashing, diffusion, and either by forced air flowing through the bed or natural convection of air if the filter medium is porous. The trickling filters usually consists of circular or rectangular beds, 1 m to 3 m deep, made of well-graded media (such as broken stone, PVC, Coal, Synthetic resins, Gravel or Clinkers) of size 40 mm to 150 mm, over which wastewater is sprinkled uniformly on the entire bed with the help of a slowly rotating distributor (such as rotary sprinkler) equipped with orifices or nozzles. Thus, the waste water trickles through the media. The filter is arranged in such a fashion that air can enter at the bottom; counter current to the effluent flow and a natural draft is produced. A gelatinous film, comprising of bacteria and aerobic microorganisms known as “Zooglea”, is formed on the surface of the filter medium, which thrive on the nutrients supplied by the waste water. The organic impurities in the waste water are adsorbed on the gelatinous film during its passage and then are oxidized by the bacteria and the other micro-organisms present therein. Wastewaters from a variety of industrial processes have been treated in trickling filters. Such industrial wastewater trickling filters consist of two types:   Large tanks or concrete enclosures filled with plastic packing or other media Vertical towers filled with plastic packing or other media

The availability of inexpensive plastic tower packings has led to their use as trickling filter beds in tall towers, some as high as 20 meters. As early as the 1960s, such towers were in use at: the Great Northern Oil's Pine Bend Refineryin Minnesota; the Cities Service Oil Company Trafalgar Refinery in Oakville, Ontarioand at a kraft paper mill.The treated water effluent from industrial wastewater trickling filters is very often subsequently processed in a clarifier-settler to remove the sludge that sloughs off the microbial slime layer attached to the trickling filter media. Currently, some of the latest trickle filter technology involves aerated biofilters which are essentially trickle filters consisting of plastic media in vessels using blowers to inject air at the bottom of the vessels, with either down flow or up flow of the wastewater.

A typical complete trickling filter system[5][6] A trickling filter consists of a bed of rocks, gravel, slag, peat moss, or plastic media over which wastewater flows downward and contacts a layer (or film) of microbials lime covering the bed media. Aerobicconditions are maintained by forced air flowing through the bed or by natural convection of air. The process involves adsorption of organic compoundsin the wastewater by the microbial slime layer, diffusion of air into the slime layer to provide the oxygen required for the biochemical oxidation of the organic compounds. The end products include carbon dioxide gas, water and other products of the oxidation. As the slime layer thickens, it becomes difficult for the air to penetrate the layer and an inner anaerobic layer is formed. The components of a complete trickling filter system are: fundamental components:     A bed of filter medium upon which a layer of microbial slime is promoted and developed. An enclosure or a container which houses the bed of filter medium. A system for distributing the flow of wastewater over the filter medium. A system for removing and disposing of any sludge from the treated effluent.

The treatment of sewage or other wastewater with trickling filters is among the oldest and most well characterized treatment technologies. A trickling filter is also often called a trickle filter, trickling biofilter, biofilter, biological filter or biological trickling filter.[5][6] Solids removal Most solids can be removed using simple sedimentation techniques with the solids recovered as slurry or sludge. Very fine solids

and solids with densities close to the density of water pose special problems. In such case filtration or ultra filtration may be required. Although, flocculation may be used, using alum salts or the addition of poly electrolytes. Oils and grease removal

A typical API oil-water separator used in many industries[7][8] Many oils can be recovered from open water surfaces by skimming devices. Considered a dependable and cheap way to remove oil, grease and other hydrocarbons from water, oil skimmers can sometimes achieve the desired level of water purity. At other times, skimming is also a cost-efficient method to remove most of the oil before using membrane filters and chemical processes. Skimmers will prevent filters from blinding prematurely and keep chemical costs down because there is less oil to process. Because grease skimming involves higher viscosity hydrocarbons, skimmers must be equipped with heaters powerful enough to keep grease fluid for discharge. If floating grease forms into solid clumps or mats, a spray bar, aerator or mechanical apparatus can be used to facilitate removal.[5] However, hydraulic oils and the majority of oils that have degraded to any extent will also have a soluble or emulsified component that will require further treatment to eliminate. Dissolving or emulsifying oil using surfactants or solvents usually exacerbates the problem rather than solving it, producing wastewater that is more difficult to treat. The wastewaters from large-scale industries such as oil refineries, petrochemical plants, chemical plants, and natural gas processing plantscommonly contain gross amounts of oil and suspended solids. Those industries use a device known as an API oil-water separatorwhich is designed to separate the oil and suspended solids from their wastewater effluents. The name is derived from the fact that such separators are designed according to standards published by the American Petroleum Institute(API). The API separator is a gravity separation device designed by using Stokes Lawto define the rise velocity of oil droplets based on their densityand size. The design is based on the specific gravitydifference between the oil and the wastewater because that difference is much smaller than the specific gravity difference between the suspended solids and water. The suspended solids settles to the bottom of the separator as a sediment layer, the oil rises to top of the separator and the cleansed wastewater is the middle layer between the oil layer and the solids.

Typically, the oil layer is skimmed off and subsequently re-processed or disposed of, and the bottom sediment layer is removed by a chain and flight scraper (or similar device) and a sludge pump. The water layer is sent to further treatment consisting usually of a Electroflotationmodule for additional removal of any residual oil and then to some type of biological treatment unit for removal of undesirable dissolved chemical compounds.

A typical parallel plate separator[9] Parallel plate separatorsare similar to API separators but they include tilted parallel plate assemblies (also known as parallel packs). The parallel plates provide more surface for suspended oil droplets to coalesce into larger globules. Such separators still depend upon the specific gravity between the suspended oil and the water. However, the parallel plates enhance the degree of oil-water separation. The result is that a parallel plate separator requires significantly less space than a conventional API separator to achieve the same degree of separation.[8][9] Activated sludge process: In general, the activated sludge process is a continuous or semicontinuous(fill and draw) aerobic method for biological wastewater treatment, including carbonaceous oxidation and nitrification. This process is based on the aeration of wastewater with flocculating biological growth, followed by separation of treated wastewater from this growth. Part of this growth is then wasted, and the remainder is returned to the system. Usually, the separation of the growth from the treated wastewater is performed by settling (gravity separation) but it may also be done by flotation and other methods. This is the most versatile biological oxidation method employed for the treatment of waste water containing dissolved solids, colloids and coarse solid organic matter. In this process, the waste water is aerated in a reaction tank in which some microbial floc is suspended. The aerobic bacterial flora bring about biological degradation of the waste into carbon dioxide and water molecule, while consuming some organic matter for synthesizing bacteria. The bacteria flora grows and remains suspended in the form of a floc, which is called “Activated Sludge”. The effluent from the reaction tank is separated from the sludge by settling and discharged. A part of the sludge is recycled to the same tank to provide an effective microbial population for a fresh treatment cycle. The surplus sludge is digested in a sludge digester, along with the primary sludge obtained from primary sedimentation. An efficient aeration for 5 to 24 hours is required for industrial wastes. BOD removal to the extent of 90-95% can be achieved in this process.

A generalized, schematic diagram of an activated sludge process .[8]

Activated sludge is a biochemical process for treating sewage and industrial wastewater that uses air (or oxygen) and microorganisms to biologically oxidize organic pollutants, producing a waste sludge (or floc) containing the oxidized material. In general, an activated sludge process includes:   An aeration tank where air (or oxygen) is injected and thoroughly mixed into the wastewater. A settling tank (usually referred to as a "clarifier" or "settler") to allow the waste sludge to settle. Part of the waste sludge is recycled to the aeration tank and the remaining waste sludge is removed for further treatment and ultimate disposal.

Oxidation ditch: This can be considered as a modification of the conventional Activated Sludge process. Waste water, after screening in allowed into the oxidation ditch. The mixed liquor containing the sludge solids is aerated in the channel with the help of a mechanical rotor. The usual hydraulic retention time is 12 to 24 hrs and for solids, it is 20-30 days. Most of the sludge formed is recycled for the subsequent treatment cycle. The surplus sludge can be dried without odour on sand drying beds.In some areas, where more land is available, sewage is treated in large round or oval ditches with one or more horizontal aerators typically called brush or disc aerators which drive the mixed liquor around the ditch and provide aeration.[1]These are oxidation ditches, often referred to by manufacturer's trade names such as Pasveer, Orbal, or Carrousel. They have the advantage that they are relatively easy to maintain and are resilient to shock loads that often occur in smaller communities (i.e. at breakfast time and in the evening).Oxidation ditches are installed commonly as 'fit & forget' technology, with typical design parameters of a hydraulic retention timeof 24 - 48 hours, and a sludge age of 12 - 20 days. This compares with nitrifying activated sludge plants having a retention time of 8 hours, and a sludge age of 8 - 12 days.

Oxidation pond: An oxidation pond is a large shallow pond wherein stabilization of organic matter in the waste is brought about mostly by bacteria and to some extent by protozoa. The oxygen requirement for their metabolism is provided by algae present in the pond. The algae, in turn, utilize the CO2 released by the bacteria for their photosynthesis. Oxidation ponds are also called waste stabilization ponds. Anaerobic digestion: Sludge is the watery residue from the primary sedimentation tank and humus tank (from secondary treatment). The constituents of the sludge undergo slow fermentation or digestion by anaerobic bacteria in a sludge digester, wherein the sludge is maintained at a temperature of 35oC at pH 7-8 for about 30 days. CH4, CO2 and some NH3 are liberated as the end products. Treatment of other organics Synthetic organic materials including solvents, paints, pharmaceuticals, pesticides, coking products and so forth can be very difficult to treat. Treatment methods are often specific to the material being treated. Methods include Advanced Oxidation Processing, distillation, adsorption, vitrification, incineration, chemical immobilisation or landfill disposal. Some materials such as some detergents may be capable of biological degradation and in such cases, a modified form of wastewater treatment can be used. Treatment of acids and alkalis Acids and alkalis can usually be neutralised under controlled conditions. Neutralisation frequently produces a precipitatethat will require treatment as a solid residue that may also be toxic. In some cases, gasses may be evolved requiring treatment for the gas stream. Some other forms of treatment are usually required following neutralisation. Waste streams rich in hardness ions as from de-ionisation processes can readily lose the hardness ions in a buildup of precipitated calcium and magnesium salts. This precipitation process can cause severe furring of pipes and can, in extreme cases, cause the blockage of disposal pipes. A 1 metre diameter industrial marine discharge pipe serving a major chemicals complex was blocked by such salts in the 1970s. Treatment is by concentration of de-ionisation waste waters and disposal to landfill or by careful pH management of the released wastewater. Treatment of toxic materials Toxic materials including many organic materials, metals (such as zinc, silver, cadmium, thallium, etc.) acids, alkalis, non-metallic elements (such as arsenic or selenium) are generally resistant to biological processes unless very dilute. Metals can often be precipitated out by changing the pH or by treatment with other chemicals. Many, however, are resistant to treatment or mitigation and may require concentration followed by land filling or recycling. Dissolved organics can be incinerated within the wastewater by Advanced Oxidation Process. Removal of Trace Metals from Wastewater during Long-Term Storage in Seasonal Reservoirs: The removal of five metals (Cu, Zn, Cr, Pb, Al) was studied in two reservoirs in series used for the seasonal storage of wastewater effluents for irrigation. The evaluation was made by two methods: (1) an anual budget which includes inputs and outputs and. (2) sediment traps. The concentrations of metals were reduced between 20 and 75%, to the base level found in unpolluted groundwater in the region.

The amount of Pb was reduced in 5%, Cu in 10%, Al in 30%, Cr in 50%, and Zn in 90%. Sedimentation has an irregular pattern due to the effect of wind induced longshore and rip-currents. The release of bottom sediments in the outflow means a direct release of trace metals and other settling pollutants and clogging particles. It is recommended to take the effluents for irrigation from the uppermost water layer, to avoid strong outflow rates which may drag out part of the sediments by hydraulic turbulence, and to locate the outlet away from the dominant wind axis. The main tools to improve the removal of trace metals in seasonal reservoirs are not the control of the age distribution of the effluents and/or the loading of the reservoirs, but the proper location, design and flow rate of the outlet. Tertiary Treatment Processes It is worthwhile to mention that the textile waste contains significant quantities of non-biodegradable chemical polymers. Since the conventional treatment methods are inadequate, there is the need for efficient tertiary treatment process. Oxidation techniques: A variety of oxidizing agents can be used to decolorize wastes. Sodium hypochlorite decolourizes dye bath efficiently. Though it is a low cost technique, but it forms absorbable toxic organic halides (AOX) [4]. Ozone on decomposition generates oxygen and free radicals and the later combines with colouring agents of effluent resulting in the destruction of colours [5]. Arslan et al. investigated the treatment of synthetic dye house effluent by ozonisation, and hydrogen peroxide in combination with Ultraviolet light [6].The main disadvantage of these techniques is it requires an effective sludge producing pretreatment. Electrolytic precipitation & Foam fractionation: Electrolytic precipitation of concentrated dye wastes byreduction in the cathode space of an electrolytic bath been reported although extremely long contact times were required. Foam fractionation is experimental method based on the phenomena that surface-active solutes collect at gas-liquid interfaces. However, the chemical costs make this treatment method too expensive. Membrane technologies: Reverse osmosis and electro dialysis are the important examples of membrane process. The TDS from waste water can be removed by reverse osmosis [8]. Reverse osmosis is suitable for removing ions and larger species from dye bath effluents with high efficiency ( up to > 90%), clogging of the membrane by dyes after long usage and high capital cost are the main drawbacks of this process. Dyeing process requires use of electrolytes along with the dyes. Neutral electrolyte like NaCl is required to have high exhaustion of the dye. For instance, in cotton dyeing, NaCl concentration in the dyeing bath is in the range of 25-30 g/l for deep tone and about 15 g/l for light tone, but can be as high as 50 g/l in exceptional cases. The exhaustion stage in reactive dyeing on cotton also requires sufficient quantity of salt. Reverse osmosis membrane process is suitable for removing high salt concentrations so that the treated effluent can be re-used again in the processing. The presence of electrolytes in the washing water causes an increase in the hydrolyzed dye affinity (for reactive dyeing on cotton) making it difficult to extract. In electro dialysis, the dissolved salts (ionic in nature) can also be removed by impressing an electrical potential across the water, resulting in the migration of cations and anions to respective electrodes via an ionic and cationic permeable membranes. To avoid membrane fouling it is essential that turbidity, suspended solids, colloids and trace organics be removed prior to electro dialysis. Electro chemical processes:They have lower temperature requirement than those of other equivalent non electrochemical treatment and there is no need for additional chemical. It also can prevent the production of unwanted side products. But, if suspended or colloidal solids were high concentration in the waste water, they impede the electrochemical reaction. Therefore, those materials need to be sufficiently removed before electrochemical oxidation [9]. Ion exchange method:This is used for the removal of undesirable anions and cations from waste water. It involves the passage of waste water through the beds of ion exchange resins where some undesirable cations or anions of waste water get exchanged for sodium or hydrogen ions of the resin [10]. Most ion exchange resins now in use are synthetic polymeric materials containing ion groups such as sulphonyl, quarternary ammonium group etc. Photo catalytic degradation: An advanced method to decolourize a wide range of dyes depending upon their molecular structure .In this process, photoactive catalyst illuminates with UV light, generates highly reactive radical, which can decompose organic compounds Adsorption: Adsorption on activated carbon occurs when a molecule is brought up to its surface and held there by physical and /or chemical forces. This process is reversible, thus allowing activated carbon to be regenerated and reused by proper application of heat and steam, or solvent. The factors that relate to adsorption capacity are: • Greater surface area produces greater adsorption capacity [e.g: Activated carbon has large surface area (500-1500 m2/g)] • Adsorptivity increases as the solubility of the solute (in solvent) decreases. Thus, for hydrocarbons, adsorption increases with molecular weight

• For solutes with ionisable groups, maximum adsorption will be achieved at a pH corresponding to minimum ionisation. • Adsorption capacity decreases with increasing temperature. One additional point to be noted is that biological activity usually takes place in a carbon bed. If the concentration of the adsorbed species is high enough and the material is biodegradable and non toxic to the bacteria, then biological activity may significantly increase the effective removal capacity. Removal through adsorption by activated carbon has been applied to non aqueous waste stream such as petroleum fraction, syrups, vegetable oils, and pharmaceutical preparations. Colour removal is the most common objective in such cases. Current waste treatment applications are limited to aqueous solutions. Resin adsorption: Waste treatment by resin involves two basic steps: (1) contacting the liquid waste stream with resin and allowing the resin to adsorb the solutes from the solution; and (2) subsequently regenerating the resins by removing the adsorbed chemicals, by simply washing with proper solvent. Thermal evaporation: The use of sodium per sulphate has better oxidizing potential than NaOCl in the thermal evaporator. The process is eco friendly since there is no sludge formation and no emission of the toxic chlorine fumes during evaporation. Oxidative decolourisation of reactive dye by persulphate due to the formation of free radicals has been reported in the literature. Electrodialysis: The electrodialysis involves the separation of an aqueous stream (more concentrated in electrolyte than the original) and a depleted stream. Success of the process depends on special synthetic membranes, usually based on ion-exchange resins, which are permeable only to a single type of ion. Cation exchange membranes permit passage only of positive ions, under the influence of electric field, while anion exchange membranes permit passage only of negatively charged ions. The feed water is passed through compartments formed by the spaces between alternating cation-permeable and anion permeable membranes held in a stack. At each end of the stack is an electrode having the same area as the membranes. A dc potential applied across the stack causes the positive and negative ions to migrate in opposite directions. This technique has already been discussed in detail under water treatment This technique has been used for desalination to produce potable water from brackish well water. In food industry electrodialysis is used for desalting whey. The chemical industry uses this technique for enriching or depleting solutions, and for removing mineral constituents from product streams. Reverse osmosis: This technique which is most widely used consists of a membrane permeable to solvent but impermeable to most dissolved species, both organic and inorganic. These devices use pressure to force the contaminated water against the semipermeable membrane. The membrane acts as a filter, allowing the water to be pushed through the pores, but restricting the passage of larger molecules that are to be removed.Cellulose acetate membranes were used in the past, but nowadayspolysulphones and polyamides are increasingly popular for use at high pH values. Because of the susceptibility of the membranes to chemical attack and fouling, and the susceptibility of the flow system to plugging and erosion, it is common to preprocess the feed water to remove oxidising materials. The reverse osmosis technique has been widely used for desalination of sea or brackish waterIt has also been successfully used in the treatment of electroplating rinsewaters, not only to meet effluent discharge standards, but also to recoverconcentrated metal salt solutions for reuse. It has also been used for treatment ofwaste stream from paper and food processing industries. Solvent extraction: Solvent extraction is the separation of the constituents of a liquid solution by contact with another immiscible liquid. If the substances comprising the original solution distribute themselves differently between the two liquid phases, a certain degree of separation will result and this may be enhanced by the use of multiple contacts.The major application of solvent extraction to waste treatment has been in the removal of phenol from by-product water produced in coal coking, petroleum refining, and chemical synthesis that involve phenol. The use of supercritical fluids (SCFs) most commonly CO2 as extraction solvent, has been one of the more promising approaches to solvent extraction. SCFs are fluids existing at or above the lowest temperature at which condensation may occur. Above the critical temperature certain fluids exhibit characteristics that enhance their solvent properties. Organic materials, which are only slightly soluble in particular solvents at room temperature, become completely miscible with the solvent when under supercritical conditions. The excellent solvent properties result from the rapid mass transfer ability and the very low density that characterises an SCF. Major advantages of SCFs are short residence times with no char formation. Some of the important application of these SCFs, has been in the extraction of organo halide pesticide from soil,

extraction of oil from emulsions used in aluminium and steel processing, and regeneration of spent activated carbon. Supercritical ethane has been used to purify waste oils contaminated with PCBs, metals and water. Distillation: Distillation is expensive and energy intensive and can probably be justified only in cases where valuable product recovery is feasible (e.g., solvent recovery). This technique has only limited application in the treatment of dilute aqueous hazardous wastes. Evaporation: Evaporation process is used for the treatment of hazardous waste such as radioactive liquids and sludges and concentrating of plating and paint solvent waste among many other applications. It is capable of handling liquids, slurries and sometimes sludges, both organic and inorganic, containing suspended or dissolved solids or dissolved liquids, where one of the components is essentially non volatile. It can be used to reduce waste volume prior to land fill disposal or incineration. The major disadvantages of evaporation are high capital and operating costs and high energy requirements. This process is more adaptable to waste waters with high concentrations of pollutants. Filtration: Filtration is well-developed economical process used in the full scale treatment of many industrial waste waters and waste sludges. Energy requirements are relatively low, and operational parameters are well defined. However it is not a primary treatment process and is often used in conjunction with precipitation, flocculation, and sedimentation to remove these solids. Flocculation: The various phenomena that occur during flocculation can be grouped in to two sequential mechanisms. • Chemically induced destabilisation of repulsive surface related forces, thus allowing particles to stick together when they touch and • Chemical bridging and physical enmeshment between the non repelling particles, allowing for the formation of large particles. Chemicals used for flocculation include alum, lime, ferric chloride, ferrous sulphate and poly electrolytes. Poly electrolytes consist of long chain, water soluble polymers such as poly acrylamides. They are used either in conjunction with inorganic flocculants, or as primary flocculating agent. The inorganic flocculants such as alum, upon mixing with water, the slightly higher pH of water causes them to hydrolyse to form gelatinous precipitates of aluminium hydroxide. It is partially because of their large surface area, they are able to enmesh small particles, and thereby create larger particles. Once suspended particles have been flocculated into larger particles, they usually can be removed from the liquid by sedimentation, provided that a sufficient density difference exists between the suspended matter and the liquid. Disinfection- water completely free of suspended sediment is treated with a powerful oxidizing agent usually chlorine, chlorine then ammonia (chloramine), or ozone. – A residual disinfectant is left in the water to prevent reinfection. – Chlorine can form harmful byproducts and has suspected links to stomach cancer and miscarriages. – Many agencies now residually disinfect with Chloramine. pH adjustment- so that treated water leaves the plant in the desired range of 6.5 to 8.5 pH units.[7][8][9][10][11] References: